OCR Types Of Bonds PDF

Types of Bonds Unit 5: Chemical Bonding Chemical Bonds: Forces that hold groups of atoms together and make them function as a unit Atoms bond to other atoms to become more stable The Octet Rule: Atoms will bond by gaining/losing or sharing enough electrons to become stable A s...

Types of Bonds Unit 5: Chemical Bonding Chemical Bonds: Forces that hold groups of atoms together and make them function as a unit Atoms bond to other atoms to become more stable The Octet Rule: Atoms will bond by gaining/losing or sharing enough electrons to become stable A stable atom has a full valence shell This typically means a full s sublevel (2 electrons) and p sublevel (6 electrons) which totals 8 valence electrons When this happens the atom becomes isoelectronic to the nearest noble gas. Electron Dot Structures: A way to show the number of valence electrons in an atom 1 = 1 e- Valence electrons are labeled as follows 5 1 4 8 X 7 3 2 6  Recall The number of valence electrons can be determined by the group the elements are in. Group # 1 2 13 14 15 16 17 18 Valence e- 1 2 3 4 5 6 7 8 E- dot structure Ionic Bonding: Occurs when an atom that loses electrons easily reacts with an atom that has a strong attraction for electrons. The participating atoms are so different that one or more electrons are transferred to form oppositely charged ions, which then have an electrical attraction for each other. Properties of Ionic Compounds: Ionic bonds are very strong Ionic compounds are solid crystals at room temperature They have high melting and boiling points Binary ionic compounds are made of a metal and a nonmetal The compound does not conduct electricity in the solid state, but does in the liquid and aqueous states Example: Sodium and Fluorine Example: Magnesium and Chlorine Example: Aluminum and Sulfur Covalent Bonding: Occurs when two atoms with similar attraction for electrons come together and share electrons Bonding results from the mutual attraction of the two positively charged nuclei for the shared negatively charged electrons Properties of Covalent Compounds: Covalent bonds are much weaker than ionic bonds Covalent compounds can be solid, liquid, or gas They have much lower melting and boiling points Covalent compounds are made of nonmetals only (and sometimes metalloids) The compound does not conduct electricity in any state Example: Hydrogen and Hydrogen Example: Oxygen and Oxygen Example: Nitrogen and Nitrogen Example: H2O Lewis Structures Unit 5: Chemical Bonding Lewis Structures: Shows how the valence electrons are arranged among the atoms in a molecule Atomic symbols represent nuclei and inner shell electrons Dashes between two symbols represent electron pairs in covalent bonds Dots adjacent to only one symbol represent unshared electrons (also called a lone pair or non-bonding pair) The key to remember when drawing Lewis structures is that each atom should have a noble gas configuration Drawing Lewis Structures: 1. Add up the total number of valence electrons in the molecule. 2. Draw a skeleton structure: ○ If there is only one atom of a specific element, that atom is in the center ○ Hydrogen can only bond to one other element ○ Be as symmetrical as possible 3. Use a line to indicate a pair of electrons to connect atoms to the central atom. 4. Arrange lone pairs of electrons as dots at right angles to satisfy octets. 5. Add up all the electrons in the drawing, it should match the number calculated in step 1. Some atoms can share multiple pairs of electrons. Single Bond: Two atoms share one pair of electrons Double Bond: a covalent bond in which two pairs of electrons are shared between two atoms Triple Bond: a covalent bond in which three pairs of electrons are shared between two atoms If the number calculated in step 5 does not match… First, change a single bond in the structure to a double bond and adjust the lone pairs on the atoms involved to maintain octets. Then, recount your electrons. If it still does not match, repeat above by adding another bond to the structure. Can be double or triple. Recount. Continue until the number matches. Resonance Structures: Some molecules can be described by more than one Lewis structure. If so, draw all possibilities. Enclose each structure in brackets and draw a double sided arrow between them. The arrows denote that the actual structure is an average of the possible structures. Polyatomic Ions: Groups of atoms that have a charge. When drawing a Lewis structure for a polyatomic ions, follow the same steps but adjust the number of electrons in step 1. If the ion is negative, add electron(s) to the total. If the ion is positive, take electron(s) away from the total. Molecular Geometry Unit 5: Chemical Bonding VSEPR Theory: Valence Shell Electron Pair Repulsion Theory Used to predict the 3-dimensional shape of molecules (molecular geometry) The electron pairs on the central atom repel each other and situate themselves as far apart as possible Lone pairs(non-bonding domains) repel more than bonding pairs/domains Linear No central atom - binary compound Polar only if the bond is polar. Linear 2 electron domains on the central atom: - 2 bonding domains - 0 non-bonding domains Nonpolar if peripheral atoms are identical. If peripheral atoms are different, it will be polar if there are polar bonds. Trigonal PLanar 3 electron domains on the central atom: - 3 bonding domains - 0 non-bonding domains Nonpolar if peripheral atoms are identical. If peripheral atoms are different, it will be polar if there are polar bonds. Tetrahedral 4 electron domains on the central atom: - 4 bonding domains - 0 non-bonding domains Nonpolar if peripheral atoms are identical. If peripheral atoms are different, it will be polar if there are polar bonds. Trigonal Pyramidal 4 electron domains on the central atom: - 3 bonding domains - 1 non-bonding domains 107° bond angle Polar only if the bonds are polar. Bent 4 electron domains on the central atom: - 2 bonding domains - 2 non-bonding domains 104.5° bond angle Polar only if the bonds are polar.